Effect of age on the saturated lecithin contents of human and rat lung tissues

Changes with age in the lecithin (especially saturated lecithin) content of human and rat lung and in lecithin synthetic activities in rat lung were examined to obtain information on lecithin metabolism in the lung in old age. In lung tissues of humans and rats, the content of saturated lecithin as a percentage of total lecithin was fairly constant (about 35%) throughout adult and old age; The percentage content in bronchial wash was 55--60% in both young and old rats. The radioactivities incorporated into lung tissue per milligram total and saturated lecithin after intravenous administration of palmitic acid3-H were similar in young and old rats. These results suggest that lung tissue contains a rather constant amount of saturated lecithin throughout adult and old age and that lecithin synthesis in the lung is still active in old age.